In the manufacturing steps of semiconductor integrated circuit devices in which an LSI is formed on a semiconductor substrate (wafer) comprised of a single crystal of silicon, a wet etching using a hydrofluoric acid (HF) solution is employed in patterning an oxide film (SiO.sub.2) of the surface of a substrate or in removing a native oxide film that is formed on the surface of the substrate in heat treatment. An etching of the surface of SiO.sub.2 is made by using a hydrofluoric acid (HF) aqueous solution or a buffered hydrofluoric acid aqueous solution (HF--NH.sub.4 F--H.sub.2 O). An etching of Si.sub.3 N.sub.4 is made by using a phosphoric acid (H.sub.3 PO.sub.4) aqueous solution. An etching of the surface of Si is made by using a hydrofluoric acid (HF)-nitric acid (HNO.sub.3) aqueous solution or a hydrofluoric acid (HF)-nitric acid (HNO.sub.3)-acetic acid (CH.sub.3 COOH) aqueous solution. When removing a metal adhered to the surface of a substrate in wiring forming steps or the like, a wet cleaning is made by using a hydrofluoric acid (HF) aqueous solution, a hydrofluoric acid (HF)-hydrogen peroxide (H.sub.2 O.sub.2) aqueous solution, or a hydrochloric acid (HCl)-hydrogen peroxide (H.sub.2 O.sub.2) aqueous solution. In these wet cleanings, in order to prevent extraneous particles from adhering to the active surface of a substrate after removing the above-mentioned oxide film or metal, it is necessary to retain the cleanliness of an etchant or a cleaning solution by, for example, circulating and filtrating the etchant or cleaning solution.
Meanwhile, such an etchant or cleaning solution is required to have a higher cleanliness as the refinement of integrated circuits is progressed. However, extraneous particles brought into a treating bath tend to increase with increasing wafer process and wafer aperture.
Although techniques of adding a surfactant into the aforementioned treating solutions have been developed, each method has the following problem. That is, even if a surfactant is dissolved until it reaches the saturated solubility, in a high concentration of HF, H.sub.2 O.sub.2, HNO.sub.3, CH.sub.3 COOH, NH.sub.4 F, HCl, H.sub.3 PO.sub.4, or an ammonium hydroxide represented by the formula [(R.sub.1)(R.sub.2)(R.sub.3)(R.sub.4)N].sup.+ OH.sup.- (R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are an alkyl group having 1 to 6 carbon atoms which may have a hydroxyl group as a substituent), when it is diluted or mixed with other chemical, the surfactant is thinned and thus fails to obtain the effect of reducing particle adhesion. In the cases where a surfactant is diluted or is added when mixing with other chemical, there are problems that much time is required and, in order to obtain a sufficient reduction effect of particle adhesion, it is necessary to add a large quantities of surfactant, causing severe foaming.
From the viewpoints as stated, the present inventors proposed a method for preventing the contamination of the surfaces of silicon wafers with fine particles by treating with a solution prepared by adding an anionic surfactant or a nonionic surfactant into a low concentration of hydrofluoric acid or the like (JP-A-41770/1994). However, this method was poor in storage and transport efficiencies. It was also unknown whether surfactants disclosed in this publication are dissolved in a high concentration into a high-level hydrofluoric acid.
Accordingly, it is an object of the present invention to provide a wafer treating solution having the following features. Specifically, when in cleaning or etching the surfaces of wafer, a specific surfactant is contained in a high concentration of HF, H.sub.2 O.sub.2, HNO.sub.3, CH.sub.3 COOH, NH.sub.4 F, HCl, H.sub.3 PO.sub.4, or an ammonium hydroxide represented by a formula: [(R.sub.1)(R.sub.2)(R.sub.3)(R.sub.4)N].sup.+ OH.sup.- (R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are an alkyl group having 1 to 6 carbon atoms which may have a hydroxyl group as a substituent), the wafer treating solution is excellent in solubility without causing severe foaming, has high storage and transport efficiencies, and exhibits an excellent action of preventing the contamination of the surfaces of wafers with fine particles when the solution is diluted at the time of use.
It is another object of the present invention to provide a wafer treating solution that exhibits an excellent action of preventing the contamination of the surfaces of silicon wafers with fine particles, in cleaning or etching the surfaces of the wafers.